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Each GRACE newsletter will explore the recyclability of a plastic used in the Large Format Print & Sign sector.
In this third edition of the GRACE newsletter we will dive into the recyclability of Polyester (PES), and more specifically the most commonly used polyester: PET. This material is the 4th most used plastic worldwide (about 8-10% of all plastic usage) with applications in mainly bottles and textile fibres. Within the LFP&S sector it finds applications as PES fabrics thanks to it being a light yet strong material therefor it is the premier choice for everything from stunning tension fabric displays and interior décor to robust flags and tear resistant paper. Crucially, the material's inherent properties allow for various printing techniques, mainly dye-sublimation and UV printing, while its thermoplastic nature positions it as a key material in the growing movement toward sustainable, recyclable graphic production.
Collection and sorting
The recycling of PET begins with a critical first step: the collection of PET-based waste. This stage is fundamental because the quality and efficiency of subsequent recycling processes depend heavily on how well the material is sorted and prepared. The GRACE project will address the logistics of PET waste collection in detail throughout 2026, focusing on optimizing collection systems to ensure a steady and clean supply of recyclable material.
Before recycling can proceed, it is essential to remove non-PET contaminants such as metallic rings, straps, zippers, and other foreign materials. These impurities can cause significant problems during processing, including damage to shredding and extrusion equipment, reduced throughput, and compromised quality of the recycled product. Contamination also increases operational costs because additional filtration or cleaning steps are required to compensate for impurities.
Modern sorting technologies play an important role in this phase. Optical sorting systems, near-infrared (NIR) scanners, and automated separation lines are increasingly used to distinguish PET from other plastics and contaminants. In some cases, manual sorting is still necessary for complex waste streams, especially in textile recycling where mixed materials are common. Proper pre-treatment not only protects equipment but also improves the purity of the recyclate, which is crucial for achieving high-quality outputs in mechanical, thermomechanical, and chemical recycling processes.
Recycling methods
1) Mechanical recycling
PET fabrics printed with sublimation inks can be recycled through mechanical recycling, which is the most established and environmentally friendly method. In this process, the yarns are carefully torn into individual fibers with minimal structural damage. These recovered fibers can then be respun into new yarns and used to manufacture fresh textiles, closing the loop in a relatively simple and energy-efficient way. However, there are important considerations. Both the use phase and the recycling process shorten the average fiber length, which can reduce spinnability and tensile strength. To compensate, many spinners blend recycled fibers with virgin PET fibers, ensuring the resulting yarn meets performance requirements for durability and quality.
One of the main challenges in mechanical recycling is colour retention. Recycled fibers keep their original colours, which typically results in fabrics that are gray or a random mix of hues. While presorting fabrics by colour can help achieve more uniform results, this is often impractical in the LFP&S sector due to the complexity and variety of printed designs. Consequently, colour limitations remain a barrier for applications that demand consistent aesthetics.
Despite these challenges, mechanical recycling remains the most sustainable option because it requires fewer processing steps, consumes less energy, and avoids chemical treatments. It is an essential part of the circular economy for PET textiles, even if design flexibility is somewhat constrained by colour variability.
2) Thermomechanical recycling
In the thermomechanical recycling process, PET is shredded into small flakes, melted, and reprocessed into pellets that can be used to manufacture new PET products. This method is widely applied in packaging and industrial sectors because it enables the material to be reintroduced into the production cycle in a relatively straightforward way.
However, thermomechanical recycling comes with a significant challenge: polymer degradation. During melting, PET is exposed to moisture and heat, which can trigger hydrolysis and lead to a reduction in molecular weight. This results in lower viscosity and diminished mechanical properties, making the recycled material less suitable for high-performance applications.
To address these issues, suppliers of thermomechanical recycling equipment offer several solutions to improve the quality of the recyclate:
- Vacuum degassing to remove volatile contaminants and moisture before extrusion, reducing hydrolytic degradation.
- High-performance filtration systems to eliminate non-melting particles and impurities that could compromise product quality.
- Polymerization units that rebuild molecular chains and restore viscosity. Alternatively, chain extenders can be added during processing to compensate for polymer breakdown. Chain extenders are widely used because they are highly efficient and cost-effective.
Colour management presents another challenge. Dyes from sublimation inks remain embedded in the PET during processing, meaning the recycled pellets retain their original colouration. While CO₂ extraction can partially remove colour, this technique is rarely applied at industrial scale due to cost and complexity. Currently, the most practical solution is to dye the recycled material black, ensuring a consistent appearance regardless of the colour of the incoming waste stream.
Thermomechanical recycling is more energy-intensive than mechanical recycling but offers greater flexibility for producing uniform pellets suitable for a variety of applications. It is an important intermediate step toward circularity, especially when combined with advanced purification technologies.
3) chemical recycling
During the chemical recycling process, PET is dissolved and broken down into its fundamental building blocks, such as monomers. These components are then fully purified and used in the polymerisation of new PET, resulting in material that is chemically identical to virgin PET. This approach is more complex than mechanical recycling but offers a significant advantage: all contaminants, dyes, and impurities are completely removed, ensuring a high-quality end product suitable for demanding applications.
Despite its benefits, chemical recycling is still relatively new and therefore limited in commercial scale. At present, only a few industrial plants are operational worldwide. For example, Jeplan operates a 22-kilotonne reactor in Japan, and Intecsa is constructing a 40-kilotonne facility in Spain. These developments mark important steps towards scaling up chemical recycling, which is expected to play a crucial role in achieving full circularity for PET in the coming years.
